CVE-2026-90043 (GCVE-0-2026-90043)
Vulnerability from cvelistv5
Published
2026-09-16 10:33
Modified
2026-10-19 08:57
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: zram: fix slot lock bit position on big-endian 64-bit The slot lock is a bit operation on the whole __lock word, which flags and ac_time alias as two u32s. On little-endian the lock bit lands in the position ZRAM_ENTRY_LOCK reserves in flags, so the aliasing works out. On 64-bit big-endian it lands in ac_time instead: with ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time from mark_slot_accessed() or slot_free() wipes out the held lock bit, letting another CPU take the same slot lock; an access time value with that bit set makes the slot look locked forever. Shift the lock bit into the flags half of the word on big-endian 64-bit.
References
Impacted products
Vendor Product Version
Linux Linux Version: 2e8ff2f51dde73a26b94aed2df4827177bd25e6e
Version: 2e8ff2f51dde73a26b94aed2df4827177bd25e6e
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/zram/zram_drv.c",
            "drivers/block/zram/zram_drv.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "052b6b2d5fe97547bd2cdb73fa894f6cfea68b11",
              "status": "affected",
              "version": "2e8ff2f51dde73a26b94aed2df4827177bd25e6e",
              "versionType": "git"
            },
            {
              "lessThan": "a8b5875741d416703e19ad8eeac6fce8a12bd6e4",
              "status": "affected",
              "version": "2e8ff2f51dde73a26b94aed2df4827177bd25e6e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/zram/zram_drv.c",
            "drivers/block/zram/zram_drv.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "lessThan": "7.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nzram: fix slot lock bit position on big-endian 64-bit\n\nThe slot lock is a bit operation on the whole __lock word, which flags and\nac_time alias as two u32s.  On little-endian the lock bit lands in the\nposition ZRAM_ENTRY_LOCK reserves in flags, so the aliasing works out.  On\n64-bit big-endian it lands in ac_time instead: with\nZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time from\nmark_slot_accessed() or slot_free() wipes out the held lock bit, letting\nanother CPU take the same slot lock; an access time value with that bit\nset makes the slot look locked forever.\n\nShift the lock bit into the flags half of the word on big-endian 64-bit."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The broken slot lock lives in the zram block driver and is reached only through local I/O: zram_submit_bio() for read/write/discard and zram_slot_free_notify() from swap. It is not in a network protocol parser, Bluetooth/WiFi path, or a physical-device driver.\nAC:L - On 64-bit big-endian kernels with CONFIG_ZRAM_TRACK_ENTRY_ACTIME, slot_free() zeros ac_time (the lock bit) immediately after slot_lock(), so exclusion is dropped on every free. An attacker who issues concurrent reads, writes, discards, or swap faults against the same zram page controls both sides of the race.\nPR:L - zram_open() and zram_submit_bio() impose no capability check. In the highest-impact setup zram is already swap or mounted scratch storage, so an unprivileged local user can induce paging or file I/O that hits the slot lock; admin-only device creation is only an environmental prerequisite.\nUI:N - After zram is configured as swap or writable storage, the attacker triggers the vulnerable path directly via memory pressure, page faults, madvise, or ordinary file I/O. No victim must mount a filesystem, open a crafted file, or otherwise participate.\nS:U - Impact is corruption of in-kernel zram table entries and zsmalloc objects on the same host. That is a standard kernel compromise and does not cross a VM, IOMMU, or other separate security authority.\nC:H - Clearing the held slot lock lets one CPU zs_free() a zsmalloc object while another still maps it in read_from_zspool()/zs_obj_read_begin(). That use-after-free of compressed-page heap objects can be reused for arbitrary kernel reads.\nI:H - The same lost exclusion allows double-free of zsmalloc handles and torn updates of slot handle and flags, so a racing writer can free an object another CPU still uses or install a new handle over a live one, enabling arbitrary kernel writes and control-flow hijack.\nA:H - Concurrent zs_free versus zs_obj_read_begin on the same handle can oops or panic the kernel, and an ac_time value that leaves the lock bit set makes later wait_on_bit_lock() sleep uninterruptibly forever on that slot."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:57:01.055Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/052b6b2d5fe97547bd2cdb73fa894f6cfea68b11"
        },
        {
          "url": "https://git.kernel.org/stable/c/a8b5875741d416703e19ad8eeac6fce8a12bd6e4"
        }
      ],
      "title": "zram: fix slot lock bit position on big-endian 64-bit",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90043",
    "datePublished": "2026-09-16T10:33:40.907Z",
    "dateReserved": "2026-09-11T19:38:34.783Z",
    "dateUpdated": "2026-10-19T08:57:01.055Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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